Polyperoxides

ABSTRACT

ORGANIC PEROXIDES OF THE FORMULA   AR (-C(-CH3)2-OOC(-CH3)3)N   WHERE N IS AN INTEGER FROM 2 TO 4, AND AR REPRESENTS A POLYVALENT ARYL GROUP CONTAINING 1 TO 3 BENZENE RINGS ARE CROSSLINKING AGENTS FOR POLYMERS.

United States Patent 3,658,914 POLYPEROXIDES George P. Gregory,Wilmington, DeL, assignor to Hercules Incorporated, Wilmington, Del.

N 0 Drawing. Continuation-impart of application Ser. No. 137,744, Sept.13, 1961, now Patent No. 3,402,205. This application June 11, 1968, Ser.No. 736,027

Int. Cl. C071 73/00 US. Cl. 260-610 R 2 Claims ABSTRACT OF THEDISCLOSURE Organic peroxides of the formula t c-ooc (CH3) 3 where n isan integer from 2 to 4, and Ar represents a polyvalent aryl groupcontaining 1 to 3 benzene rings are crosslinking agents for polymers.

This application is a continuation-in-part of application Ser. No.137,744, filed Sept. 13, 1961 now Pat. No. 3,402,205.

This invention relates to organic peroxides having low residual odorafter thermal decomposition and are particularly useful in thecrosslinking of polymers in that they do not impart objectionable odorsthereto.

The organic peroxides of this invention are organic polyperoxides inwhich at least two t-alkylperoxy-a-isopropyl radicals are attached to anaryl group or nucleus. The aryl group contains one or more aryl rings towhich the t-alkylperoxy-a-isopropyl radicals are attached.

The organic polyperoxides of this invention are readily prepared, forexample, by the steps of: (1) oxidation of a polyisopropyl aryl compoundcontaining at least two isopropyl groups attached to the aryl group, andcapable of oxidation to a hydroperoxide, by contacting with elernentaryoxygen until at least two hydroperoxide groups are formed; (2) reductionof the hydroperoxy compound to the corresponding hydroxy compound; and(3) reaction of the poly(hydroxyisopropyl)aryl compound containing atleast two a-hydroxyisopropyl groups with a chemical equivalent quantityof t-alkyl hydroperoxide until an organic peroxide having at least twot-alkylperoxyisopropyl groups attached to the aryl group is produced.The product of this process is useful as a crosslinking catalyst.Specific compounds which can be isolated and defined by chemical formulacan also be produced by purification of the intermediates formed in eachof the steps and a specific aryl compound to which at least twoot-hydroxyisopropyl groups are attached may be made by the above stepsand reacted with at least two moles of t-alkyl hydroperoxide to producea specific aryl compound having at least two t-alkylperoxyisopropylgroups attached thereto.

The reaction steps (1) and (2) of this invention are represented by thefollowing equation:

a: a e A: ca ---9 A: c-ooi-i Ar c-ou Eu 0 on ca;

3 r1 3 R n and the last step is represented by the following equation:

E P A! -01: or (a) poon-4 Ar c-ooc (a) 3 +nu o CH CH rt 3 n.

"ice

where n represents at least two and not more than four, and where Arrepresents a polyvalent (n-valent) aryl group, and (R) C represents at-alkyl group having 4 to 12 carbon atoms. This last reaction is carriedout by heating the reactants with an acid-acting condensation catalystat 50-120 C., preferably 60-100 C. in a volatile organic solvent atreflux while azeotropically distilling ofi the water, liberated in thereaction. Mixtures, as well as specific poly(u-hydroxyisopropyl)arylcompounds, may be reacted with t-alkyl hydroperoxide to produce specificperoxides of this invention, however, and their structures are welldefined. The general procedure of this step is described in US.2,668,180.

The preparation of aryl compounds of the formula Hit].-

by alkylation of aryl compounds with propylene so as to introduce atleast two isopropyl groups attached to the aryl nucleus so as to producesuch a compound is well known. Aluminum chloride and boron trifluorideare typical catalysts for this reaction. The isomers produced in thisreaction need not be separated, but can be separated if desired.

Oxidation of these isopropyl aryl compounds to produce hydroperoxidesthereof by means of elementary oxygen is well known in the art asexemplified by US. 2,438,125; US. 2,547,938; US. 2,548,435; US.2,632,774; US. 2,664,447; US. 2,856,433 and Re. 23,916.

The hydroperoxides formed in the oxidation may be reduced by reactionwith metal sulfides, by reaction with hydrogen and a catalyst,electrolytically by an electric current or by an electromotive couple,by thermal decomposition in the presence of alkalies or by giving upoxygen to a receptive hydrocarbon in the presence of heavy metalcatalysts, sodium alkoxides or sodium hydroxide. The latter method ispreferable, since the oxidation step and the hydroperoxide reductionstep may be carried out simultaneously simply by contacting thepropylated aryl compound with elementary oxygen in the presence ofstrong alkali such as sodium hydroxide.

The process of preparing the organic peroxides of this invention isillustrated by the following examples in which all parts and percentagesare by weight.

EXAMPLE 1 Refinery gas (3 parts propylene:l part ethylene) was passedinto 117 parts benzene containing 73.5 parts sulfuric acid at about 5 C.until 126 parts of the refinery gas had reacted. The eflluent gascontained propylene and ethylene in a lower ratio. The liquid reactionmixture was poured into cold water, washed with water, and distilledfrom lime .The diisopropylbenzene fraction was recovered, mixed with 0.4mole percent of AlCl at 40 C. The temperature was then raised to 60-65C. for /2 hour to isomerize the diisopropylbenzene to increase theamount of meta isomer. This reaction mixture was washed with water andthen with alkali and distilled to separate the m-diisopropylbenzene.

To a vigorously stirred mixture of 1,000 parts m-diisopropylbenzene and500 parts 2% aqueous sodium hydroxide was added a finely divided streamof air while maintaining a temperature of 60-80 C. When theconcentration of hydroperoxide reached 45%, the hydroperoxide solutionwas separated from the aqueous sodium hydroxide solution and addedgradually with rapid agitation to a solution of 275 parts sodium sulfidenonahydrate in 830 parts water while heating at -l00 C. After 3 hoursheating, the hydroperoxide content was substantially zero. The aqueouslayer was then separated, and the organic layer was made slightlyalkaline with sodium hydroxide and steam distilled to remove about 50%of the organic material. The residual organic material was crystallized,and 350 parts crystalline m-bis(hydroxyisopropyl)benzene was recovered.

A mixture of 49.5 parts m-bis(hydroxyisopropyl)benzene, 54.7 partst-butyl hydroperoxide, 130 parts benzene, and 130 parts anhydrousethanol, in which 1.8 parts p-toluene sulfouic acid was dissolved, washeated at 70- 80 C. with stirring for 14 hours under a reflux condenserfitted for water removal from the refluxing azeotrope. The progress ofthis reaction was followed by measuring the rate of water evolution.After 3.6 hours, the reaction was essentially complete, and the peroxidecontent was essentially 90% in the form of peroxide. The whole reactionmixture was washed with several portions of 5% sodium hydroxide untilneutral, and then with water to remove the alcohol and residual alkali.The benzene was distilled off from the organic layer under reducedpressure. The residue was m-bis(t-butylperoxyisopropyl)benzene ofpractical grade.

EXAMPLE 2 m-Diisopropylbenzene was prepared by alkylation of benzene asin Example 1 and was separated by fractional distillation from itsisomers. This m-diisopropylbenzene was then oxidized by contacting withair while vigorously stirring in the presence of aqueous concentratedsodium hydroxide. The hydroperoxide formed was continuously reduced inthis process by reaction with excess m-diisopropylbenzene and alkali,and the last of the hydroperoxide Was reduced by continuing to heatwithout addition of oxygen so as to avoid further hydroperoxideformation. The m-bis(hydroxyisopropyl)benzene so formed was concentratedby steam distilling unreacted m-diisopropylbenzene from the reactionmixture and, on cooling the m-bis(hydroxyisopropyl)benzene, crystallizedout.

A mixture of 48 parts m-bis (hydroxyisopropyl)benzene, 54 parts 89%t-butyl hydroperoxide, 520 parts anhydrous alcohol, 0.7 part p-toluenesulfonic acid, and parts hexane was heated at 70-79 C. under reflux withcontinuous removal of water evolved. At the end of 5 hours, waterevolution had ceased and only 4% of the original hydroperoxide remained.The product recovered as in Example 1 amounted to 62.4 parts. This wasanalyzed by means of Craig countercurrent extraction between isooctaneand acetonitrile. There was a polar peak amounting to about 16%containing m-t-butylperoxyisopropyl(hydroxyisopropyl)benzene and anonpolar peak of about 82% containing mostlym-bis(t-butylperoxyisoproyl)benzene (97% :2) was characterized by anultraviolet absorption spectrum showing a single peak at 260 m and by aninfrared absorption having no OH or CO absorption bands. It analyzed:71.8% C, 10.4% H, and 18.3% O;-n1ol. wt. (acetone), 328 correspondingfairly well with that for C H O Its physical characteristics are: d(supercooled) =0.936l; n (super cooled)=1.47l8; M.P. 4952 C.

EXAMPLE 3 The procedure of Example 1, repeated using biphenyl in placeof benzene in the propylation step, yields as final product a peroxidicmaterial containing a compound identified asbis(t-butylperoxyisopropyl)diphenyl.

EXAMPLE 4 The procedure of Example 1, repeatedusing diphenyl ether inplace of benzene in the propylation step, yields as final product aperoxidic material containing a compound identified asbis(t-butylperoxyisopropyl)diphenyl ether.

EXAMPLE 6 The procedure of Example 1, repeated using durene in place ofbenzene in the propylation step, yields as final product a compoundidentified as bis(t-butylperoxyisopropyl) durene.

EXAMPLE 7 The procedure of Example 1, repeated using benzene andpropylating to the stage of introduction of three isopropyl groups sothat the product oxidized to the hydroperoxide was a triisopropylbenzenemixture, yields as final product a peroxidic material rich in isopropylbis(tbutylperoxyisopropyl)benzene, but also containing sometris(t-butylperoxyisopropyl)benzene, some isopropenylbis(t-butylperoxyisopropyl)benzene, and some hydroxyisopropylbis(t-butylperoxyisopropyl)benzene in addition.

EXAMPLE 8 In a round-bottom flask fitted with a reflux condenser havinga water-takeofi device was placed 19.8 parts m-bis(hydroxyisopropyl)benzene of 9 8% purity, 71.5 parts pmenthylhydroperoxide mixed isomers of 53% purity in hydroperoxide content, 52.0parts anhydrous ethanol, and 0.24 part p-toluene sulfonicacid(monohydrate). This mixture was refluxed at 71-75 C. with watertakeoff for 20 hours, additional portions of 0.1 part each of p-toluenesulfonic acid being added every 4 hours. To this reaction mixture wasthen added 8 8 parts benzene, and the solution was neutralized with 5%sodium hydroxide solution and Washed with Water until sodium-free. Thesolvent was then distilled off, and 54.1 partsbis-m-(p-menthylperoxyisopropyl)benzene was recovered.

EXAMPLE 9 A solution of 15.8 parts m-bis(hydroxyisopr0pyl)ben zene of98% purity, 39 parts p-menthane hydroperoxide of 84% purity and 0.3 partp-toluene sulfonic acid monohydrate in 17 parts hexane was heated atabout C. for 6 hours, a second portion of 0.5 part p-toluene sulfonicacid being added after the first 3 hours of heating. The water ofreaction separated from the hexane solution. The organic solution wasthen neutralized with 5% sodium hydroxide and washed sodium-free withwater. After distilling off the hexane, there was obtained 54 parts of amixture containing 60.8% m-bis(p-rnenthylperoxyisopropyl) benzene. Therefractive index of this residue was n 1.498, d =0.978.

EXAMPLE 10 A solution of 2.5 parts 1,3,5-tris(hydroxyisopropyl)-benzene, prepared by oxidation of 1,3,5-triisopropylbenzene with air inthe presence of a sodium hydroxide dispersion and reduction of the1,3,5-tris(hydroperoxyisopropyl)benzene, and 3.6 partst-butylhydroperoxide in 8 parts anhydrous ethanol was heated at 72-75 C.with 0.1 part p-toluene sulfonic acid for 6 hours. The reaction mixturewas dissolved in 40 parts benzene, neutralized with 5% aqueous sodiumhydroxide, and washed with water until sodium-free. The residue afterdistilling ofi the solvent was a viscous liquid analyzing 63% 1,3,5-tris(t-butylperoxyisopropyl)benzene.

In this preparation, 1,3,5-tris(hydroxyisopropyl) benzene made by othermethods, such as by reaction of methyl magnesium bromide with1,3,5-triacetylbenzene, works equally well in the reaction with t-butylhydroperoxide for production of the poly(t-butylperoxyisopropyl)arylcompounds having two or more peroxide groups attached to the arylnucleus.

EXAMPLE 11 p-Isopropylbenzene sulfonyl chloride was prepared in about90% yield by adding 350 parts chlorosulfonic acid gradually to a stirredsolution of parts cumene in 375 parts methylene chloride at -10 C. Theresulting mix ture was washed with water and dried. From this mixture,199 parts p-isopropylbenzene sulfonyl chloride was recovered.

Bis(p-isopropylphenyl)sulfone was prepared by adding 102 parts cumene in75 parts methylene chloride to a stirred mixture of 110 parts aluminumchloride in a solution of 185.3 parts p-isopropylbenzene sulfonylchloride in 300 parts methylene chloride at 05 C. This reaction mixture,after warming to room temperature and stirring for a 16-hour period, wasdiluted with water and washed with 4% aqueous sodium hydroxide and withwater. After removal of the methylene chloride, 248 parts bis(p-isopropylphenyl) sulfone was recovered. Its melting point was 109110 C.

Bis (p-isopropylphenyl)sulfone was oxidized tobis(p-ahydroxyisopropylphenyl)sulfone by stirring vigorously a mixtureof 100 parts of bis(p-isopropylphenyl)sulfone and 50 parts of 50%aqueous sodium hydroxide at 105138 C. for 14 hours in an oxygenatmosphere at atmospheric pressure. The product was purified bysubjecting to countercurrent distribution between ether and ethyleneglycol. The most polar part was then crystallized from ether. Therecrystallized bis(p ot-hydroxyisopropylphenyl)sulfone melted at 139140C.

Bis(p-ot-tbutylperoxyisopropylphenyl)sulfone was prepared by heating 22parts bis(p-a-hydroxyisopropylphenyl)sulfone and 100 parts t-butylhydroperoxide in 100 parts heptane at 4969 C. under reduced pressure,with 0.38 part p-toluene sulfonic acid and about 0.2 part 96 sulfuricacid. The reaction was stopped when water was no longer azeotropicallydistilling off. The resulting solution was freed of acid by washing with8% aqueous sodium hydroxide and then with water. Infrared and iodometricanalyses indicate a 30% yield of 'bisperoxide.

EXAMPLE 12 Dicumylmethane was prepared by mixing 180 parts trioxane and120 parts zinc chloride with 862 parts cumene and passing hydrogenchloride gas into the mixture at -35 C. until saturated with hydrogenchloride. The aqueous zinc chloride phase was separated, and 15 partsanhydrous aluminum chloride and parts nitromethane were added. Thereaction mixture was allowed to react 1 6 hours at C., and 5 parts morealuminum chloride was added and reaction was continued with stirringfirst at 37 C. and finally at 45 C. The final reaction mixture waswashed with water and with aqueous sodium hydroxide and dried. Thisproduct, after removing cumene, was a mixture of isomers ofdicumylmethane of which 75.1% was p-, p'-; 18.8% was m-, p-; 5.1% wasm-, m-; and 1.0% was o-, p'-.

This dicumylmethane mixture was oxidized by contacting vigorously 65parts of the mixture and 3 parts calcium hydroxide with oxygen gas atatmospheric pressure for 13.5 hours at 120-140 C. The lime was removedby filtration, and the product was purified by distribution betweenether and ethylene glycol. The most polar fraction amounting to 32 partswas bis(ot-hydroxyisopropylphenyl)ketone.

Bis(a-t-butylperoxyisopropylphenyl)ketone was prepared by heating partsof the above his (a-hydroxyisopropylphenyl)ketone with 56.3 parts 82%t-butyl hydroperoxide, and 0.57 part p-toluenesulfonic acid in 100 partsof heptane at 4850 C. under reflux with water collection for 3.5 hours.The reaction was terminated when no more water was evolved. The reactionmixture was washed free of acid and excess t-butylhydroperoxide withwater and 8% aqueous sodium hydroxide solution. After removal of theheptane, the bis(ot-t-butylperoxyisopropylphenyl) ketone was recoveredas a product, the yield of which was shown by infrared and iodometricanalyses to be 19.2%. This product may also be calledbis(u-t-butylperoxyisopropyl)benzophenone.

EXAMPLE 13 2,2-diphenylpropane was prepared by adding 135 partsa-methylstyrene dropwise to a saturated solution of hydrogen chloride in240 parts benzene at O-S" C., and then adding more hydrogen chloride gasuntil absorption stopped, and then adding this solution to 2400 partsbenzene saturated with hydrogen chloride, and containing 24 partsaluminum chloride and 30 parts nitromethane .at 0 C. and stirring for1.5 hours at O-5 C. The 2,2-d1phenylpropane was recovered by washing thereaction product with water, distilling off the benzene and then washlngwith 96% sulfuric acid and finally with water. The yield was about 218parts.

2,2-bis(p-acetylphenyl)propane was produced by adding 49 parts2,2-diphenylpropane dropwise with stirring at 5l0 C. to a mixture of 43parts acetyl chloride and 73.5 parts aluminum chloride in 120 partsnitrobenzene and then warming gradually to room temperature, and finallyheating at -95 C. for 3 hours, and the product was recovered by washingwith water and finally distilling. The yield of2,2-bis(p-acetylphenyl)propane was 51.1 parts having a purity of betterthan 92%. The melting point of a purified sample was 67 C.

2,2-bis(et-hydroxy-p-isopropylphenyl) propane was prepared by adding 28parts 2,2-bis(p-acetylphenyl)propane in 50 parts ether gradually tomethyl magnesium iodide in ether prepared by reacting 5.35 partsmagnesium turnings with 31.24 parts methyl iodide in 40 parts ether andfinally heating at 50 C. for one hour. The product was recovered bywashing the ether solution with aqueous ammonium chloride and then withwater followed by distilling off the ether. The yield of2,2-bis(a-hydroxy-p-isopropylphenyl)propane was 28.6 parts, a sample ofwhich, after crystallization from a hexane-ether-acetone mixture, meltedat -116 C.

2,2-bis a-t-butylperoxy-p-isopropylphenyl) propane was prepared byrefluxing at 50 C. a heptane solution of 14 parts2,2-bis(ot-hydroxy-p-isopropylphenyl)propane, M.P. 115-116 C., 25 parts82% t-butylhydroperoxide and 0.25 part p-toluenesulfonic acid in 80parts heptane with azeotropic removal of water until water separationceased. The resulting 2,2 bis(ut-t-butylperoxy-p-isopropylphenyl)propanewas recovered by washing with 8% sodium hydroxide solution and then withwater, and then distilling off the heptane. It was a solid having apurity by peroxide analysis of 84.4%.

The poly(t-alkylperoxyisopropyl)aryl compounds of this invention havethe general formula a $-OOCR3 CH3 where n is at least 2 and not morethan 4, Ar is an aryl nucleus containing 1 to 3 benzene rings, and the Rgroups are individual cyclic or acyclic alkyl groups which may be thesame or different and, when two are taken together, may constitute adivalent cycloalkyl group of which the carbon to which the other R groupis attached is a ring member. The aryl nucleus of these compoundsincludes the benzene, naphthalene, phenanthrene, diphenyl, and terphenylrings, which may be in part substituted with alkyl groups, and includesalso compounds of the general formula [Ar'xAr"5 where Ar and Ar" may bean alkyl substituted or unsubstituted benzene, naphthalene,phenanthrene, diphenyl or terphenyl ring, and x is a copulating group.The operable copulating groups are -O-, CH (CH C=, =CO, =SO

2: i 1| 0 41-, and 0 CCHgCH2u:O- The isopropyl groups may be on adjacentcarbons or may be separated from each other, and may even be in widelyseparated positions in the aryl group, as when they are attached todifferent rings.

The Ar group in the compounds of this invention is broad in scope, sinceits essential purpose is to carry the groups and provide an odorlessresidue in the products of decomposition of the peroxides. Thepoly(t-alkylperoxyisopropyDaryl compounds will thus have the generalformula and C H x-C H E, where x is one of the copulating groups setforth above; (3) containing 3 benzene rings, C H (phenanthrene), C H(terphenyl) and the corresponding aryl groups containing lower alkylsubstituents of 14 carbons where such substitution is possible.

The aryl group containing two benzene rings will have the rings fused toeach other as in the naphthalene and anthracene groups, attached to eachother by a common bond as in the diphenyl group, or separated from eachother by at least one atom as in the Ar'-xA1-" groups.

The polyisopropyl aryl compounds which are oxidized in the first step ofthe process of this invention may be made by propylation of an arylcompound of the formula Ar--H where Ar represents the same aryl nucleias set forth above, or they may be made by indirect means, particularlyin the case of compounds of the formula Ar'x-Ar" where the x group isintroduced by coupling =Ar'(C I-I-;) or Ar(=C I-I-,) by known means, Inbeing a number indicating the number of isopropyl groups present. Wherex is O, CH (CH C= or CO, the isopropyl groups may be introduced bypropyl ation of the unpropylated compounds. Where x is O, this linkagemay be put in last by the same type of reactions as are used forproducing diphenyl ether, such as for example, by heating a sodiumisopropylphenoxide with an isopropylchlorobenzene. For the case where xis z,

Ar (C3H7) CH Cl may be reacted with Ar(C H in the presence of AlCl or BFFor the case where x is (CH O==, Ar'(C I-I may be reacted with acetonein the presence of sulfuric acid. For the case where x is CO, Ar'(C Hmay be reacted with phosgene in the presence of A101 or Ar'(C H COCl maybe reacted with Ar(C H in the presence of AlCl or BF For the case wherex is --SO;,---, a sulfonyl chloride,

Ar ('cgfiq) SO CI is reacted with Ar"(C H For the case where 8 an acid,Ar(C H 'COOH, may be esterified with a phenol, Ar(C H OH. For the casewhere a phenol, Ar(C I-I OH, may be reacted with succinic acid or itsanhydride. In all of these cases, it is understood that all or part ofthe isopropyl groups may be in a single moiety of the aryl compound. Inall cases, the sum of m values in both moieties equals n.

In the oxidation to the hydroperoxide and in reduction of thehydroperoxide to the poly(hydroxyisopropyl)- aryl compounds, as well asin the reaction of the latter with the tertiary alkyl hydroperoxide,there is no significant change in the Ar group through the various stepsother than those indicated above. Thus, diisopropylbenzene is oxidizedto diisopropylbenzene dihydroperoxide, and this is reduced to thexylylene dialcohol. Similarly, triisopropylbenzene may be oxidized to amixture containing a small amount of monohydroperoxide, a small amountof trihydroperoxide, and a large amount of dihydroperoxide, and this onreduction will produce a corresponding mixture of carbinols which isreacted with talkyl hydroperoxide to give a mixture rich in the organicperoxides of this invention, which has the advantageous properties ofthe pure peroxides.

The t-alkyl group introduced into the compounds of this invention by thetalkyl hydroperoxide is illustrated by the following: t-butyl, t-amyl,t-hexyl (3 isomers), theptyl (6 isomers), t-octyl, t-nonyl, t-decyl,t-dodecyl, tcyclohexyl (e.g., l-methylcyclohexyl), p-menthyl (l-, 7- and8-isorners), pinanyl (pinane ring). In each case, it is thetertiary-alkyl hydroperoxide which is reacted with thepoly(hydroxyisopropyl)aryl compound to produce the poly(t-alkylisopropyl)aryl compound of this invention.

The acid-acting condensation catalyst used in the peroxide condensationstep of the process of this invention is any of the well-known,acid-acting, condensation catalysts, such as Friedel-Crafts typecatalysts including B1 ether complexes of BF organic acid complexes ofBF halides of metals whose hydroxides are amphoteric, such as AlCl ZnClSnCl TiCl etc., and mineral acid condensation catalysts such as HF, H81H 50 H PO organic sulfonic acids, organic acid sulfates, aromaticsulfonic acids, including benzene, toluene, and naphthalene sulfonicacids. A catalyst, such as the organic sulfonic acids, which is solublein the solvent vehicle of the reaction, is preferred.

The amount of acid-acting condensation catalyst will be small so as toavoid degradation of the peroxide, the useful amount being in the rangeof 0.001% to 1.0% based on the weight of the reactants.

In carrying out the process of this invention, a slight excess (up toabout 10%) of t-alkyl hydroperoxide is used for best yields.

A solvent boiling in the range of 50-420 C. is advantageously used inthe peroxide-forming step of the process of this invention so as todrive off the water produced in the reaction. The solvent may beselected from the following: saturated aliphatic hydrocarbons such as apentane cut, a hexane cut, a heptane cut, a gasoline cut or a naphthacut, benzene, toluene, xylenes, cumene, carbon tetrachloride, ethylenechloride, and the like. If desired, reduced pressure may be used to aidin azeotropic distillation of the water produced. In order to promotehomogeneity of the reaction mixture, ethanol is also advantageouslyadded.

The polymers which may be cured by means of the poly(t-al'kylperoxy)arylcompounds of this invention are: natural rubber, polyethylene,polyisoprene, poly(vinyl chloride), polystyrene, copolymers of ethyleneand propylene ('EPR), cis-4-polybutadiene, poly(chloroprene),poly(dimethyl siloxane), GR-S (butadiene-styrene copolymer) and GR-N orBuna-N (butadiene-acrylonitrile copolymer).

10 All of the peroxides of the specific examples are good ReferencesCited crosslinking agents for both natural and black-filled low densitypolyethylene. All of the peroxides have about the UNITED PATENTS samehalf-life. None of the cured polymers had a dis- 3,118,866 V1964Gregonan 250*610 R UX agreeable odor. 5 3,402,205 9/1968 Gregory260'-61O 'What I claim and desire to protect by Letters Patent is:

1. 2,2 bis(alpha t butylperoxy-p-isopropylphenyl)- HOWARD MARS 'PnmaryExaminer propane.

2. 1,3,5 tris[alpha,alpha dimethyl alpha (t-butyl- CLperoxy)methyl]benzene. 10 260-41 R, 80 R, 82.1, 82.3, 94.2, 94.91 A,590, 607 A

